Apparatus and method for forming three-dimensional objects using two-photon absorption linear solidification

Abstract

An apparatus and method for making a three-dimensional object from a solidifiable material using two photon absorption is described. The use of two photon absorption allows for the creation of a non-solidification zone beneath the exposed surface of a solidifiable material so that no separation is required between the most recently solidified layer of the object and a substrate such as a glass, a film, or a glass/film combination. In addition, when used with a linear scanning device, two photon absorption causes solidification to occur within a small spot area, which provides a means for creating larger, higher resolution objects than DLP systems or laser systems that use single photon absorption.

What is claimed is: 
     
         1 . An apparatus for making a three-dimensional object from a solidifiable material, comprising:
 a selectively activatable laser having a first wavelength;   a linear scanning assembly comprising two linear scanning devices;   an optical fiber beam splitter having an input and two outputs, wherein each output is connected to a respective one of the linear scanning devices, wherein the linear scanning devices are movable along a travel axis and each scan along a scanning axis a respective beam of solidification energy received from a corresponding one of the optical fiber splitter outputs;   a source of solidifiable material having an exposed surface;   wherein the linear scanning devices are configured such that their respective beams intersect at a focal point within the solidifiable material that is spaced apart from the exposed surface along a build axis.   
     
     
         2 . The apparatus of  claim 1 , wherein the focal point is spaced apart from the exposed surface of the solidifiable material by a distance that is no less than about 0.2 mm from the exposed surface of the solidifiable material. 
     
     
         3 . The apparatus of  claim 1 , wherein the selectively activatable laser has a pulse width of less than about 10 −8  seconds. 
     
     
         4 . The apparatus of  claim 1 , wherein the selectively activatable laser has a wavelength between about 700 nm and about 800 nm. 
     
     
         5 . The apparatus of  claim 1 , wherein the laser power at the focal point is at least about 1 GW. 
     
     
         6 . The apparatus of  claim 1 , wherein the selectively activatable laser has an average output power of at least about 150 mW. 
     
     
         7 . The apparatus of  claim 1 , wherein the solidifiable material comprises a multiphoton sensitizer. 
     
     
         8 . The apparatus of  claim 1 , wherein the solidifiable material comprises a photoinitiator having an excitation wavelength range that includes one half of the first wavelength. 
     
     
         9 . The apparatus of  claim 1 , wherein when the input of the optical fiber beam splitter receives laser light of the first wavelength, the two outputs each transmit light having second wavelengths that are substantially equal. 
     
     
         10 . The apparatus of  claim 1 , wherein when the input of the optical fiber beam splitter receives laser light of a first intensity, the two outputs each transmit light having a second intensity that is about one half of the first intensity. 
     
     
         11 . The apparatus of  claim 1 , wherein the linear scanning devices are configured such that their respective beams intersect to define a spot having a diameter of no more than about 20 microns at the focal point. 
     
     
         12 . The apparatus of  claim 1 , wherein the selectively activatable laser is a Ti:Sapphire laser. 
     
     
         13 . The apparatus of  claim 1 , wherein the power of each respective beam is insufficient to solidify the solidifiable material between the focal point and the exposed surface of the solidifiable material. 
     
     
         14 . The apparatus of  claim 1 , wherein the linear solidification devices are spaced apart from and located above the source of the solidifiable material along the build axis. 
     
     
         15 . The apparatus of  claim 1 , wherein the linear solidification devices are spaced apart from and located beneath the source of the solidifiable material along the build axis. 
     
     
         16 . The apparatus of  claim 1 , wherein multi-photon-induced polymerization occurs at the focal point. 
     
     
         17 . The apparatus of  claim 1 , wherein the solidifiable material comprises a photoinitiator, and the photoinitiator absorbs the energy of two photons at the focal point. 
     
     
         18 . An apparatus for making a three-dimensional object on a build platform by solidifying a solidifiable material contained in a source of solidifiable material, the apparatus comprising:
 a selectively activatable laser configured to selectively transmit laser light of a first wavelength;   a linear scanning device comprising a rotatable polygonal mirror and an optical system, wherein the selectively activatable laser is in optical communication with the rotating polygonal mirror, the linear scanning device travels along a travel axis, and the optical system comprises at least one first mirror and second mirror between the rotating polygonal mirror and an exposed surface of the solidifiable material, the at least one first mirror and second mirror have a rotationally symmetric curved mirror surface about their optical axis, at least one of the first and the second curved mirror surface has an aspheric shape, and the at least one first and second mirror have an off-axis decentered aperture and are offset in position with respect to one another in a direction perpendicular to a scanning axis,   wherein the exposed surface of the solidifiable material is located between the linear scanning device and the build platform, when the selectively activatable laser is activated while the rotatable polygonal mirror rotates, laser light is deflected from the rotatable polygonal mirror through the optical system to scan a focal point of solidification energy within the solidifiable material and along the scanning axis, the focal point is spaced apart from the exposed surface of the solidifiable material along a build axis, the solidifiable material solidifies at the focal point and does not solidify between the exposed surface of the solidifiable material and the focal point.   
     
     
         19 . The apparatus of  claim 18 , wherein the laser is stationary as the linear scanning device travels along the travel axis. 
     
     
         20 . The apparatus of  claim 18 , wherein the laser travels along the travel axis as the linear scanning device travels along the travel axis. 
     
     
         21 . The apparatus of  claim 18 , wherein the laser has a pulse width of less than about 10 −8  seconds. 
     
     
         22 . The apparatus of  claim 18 , wherein the selectively activatable laser has a wavelength between about 700 nm and about 800 nm. 
     
     
         23 . The apparatus of  claim 18 , wherein the laser power at the focal point is at least about 1 GW. 
     
     
         24 . The apparatus of  claim 18 , wherein the selectively activatable laser has an average output power of at least about 150 mW. 
     
     
         25 . The apparatus of  claim 18 , wherein the solidifiable material comprises a multiphoton sensitizer. 
     
     
         26 . The apparatus of  claim 18 , wherein the solidifiable material comprises a photoinitiator having an excitation wavelength range that includes half of the first wavelength. 
     
     
         27 . The apparatus of  claim 18 , wherein when the selectively activatable laser is activated, the focal point has a spot diameter of no more than about 20 microns. 
     
     
         28 . The apparatus of  claim 18 , wherein the selectively activatable laser is a Ti:Sapphire laser. 
     
     
         29 . The apparatus of  claim 18 , wherein the linear scanning device is spaced apart from and located above the source of the solidifiable material along the build axis. 
     
     
         30 . The apparatus of  claim 18 , wherein the linear scanning device is spaced apart from and located beneath the source of the solidifiable material along the build axis. 
     
     
         31 . The apparatus of  claim 18 , wherein multi-photon-induced polymerization occurs at the focal point. 
     
     
         32 . The apparatus of  claim 18 , wherein the solidifiable material comprises a photoinitiator, and the photoinitiator absorbs the energy of two photons at the focal point. 
     
     
         33 . The apparatus of  claim 18 , wherein the shape of the first and second mirror is optimized for telecentricity less than 5 degrees and line bow less than +20/−20 microns for mechanical scan angles of +/−16 degrees, and a spot size variation less than 5%. 
     
     
         34 . The apparatus of  claim 18 , wherein the other one of the at least one first and second curved mirror surface has a spherical shape. 
     
     
         35 . The apparatus of  claim 18 , wherein the other one of the at least one first and second curved mirror surface also has an aspheric shape. 
     
     
         36 . The apparatus of  claim 18 , wherein the optical system consists of the first mirror and the second mirror. 
     
     
         37 . An apparatus for making a three-dimensional object from a solidifiable material, comprising:
 a solidifiable material container containing the solidifiable material such that the solidifiable material has an exposed surface;   a selectively activatable laser;   a linear scanning device operatively connected to the laser, wherein the linear scanning device is movable along a travel axis and scans solidification energy received from the laser in linear patterns along a scanning axis, and the linear patterns have a focal point spaced apart from the exposed surface of the solidifiable material along a build axis.   
     
     
         38 . The apparatus of  claim 37 , wherein the laser is a femtosecond laser. 
     
     
         39 . The apparatus of  claim 37 , wherein the linear scanning device comprises a rotatable polygonal mirror configured such that when the linear scanning device moves along the travel axis, the rotating polygonal mirror rotates in a plane perpendicular to the travel axis and parallel to the scanning axis. 
     
     
         40 . The apparatus of  claim 37 , wherein the solidifiable material comprises a photoinitiator that is capable of simultaneously absorbing two photons of energy at the focal point but not between the focal point and the exposed surface of the solidifiable material. 
     
     
         41 . A method of making a three-dimensional object from a solidifiable material, comprising:
 providing a source of the solidifiable material, wherein the solidifiable material comprises a photoinitiator;   selectively activating a laser in optical communication with a rotating polygonal mirror as the rotating polygonal mirror travels along a travel axis to scan laser energy in a linear pattern along a scanning axis within the solidifiable material such that the photoinitiator absorbs two photons at a selected distance from an exposed surface of the solidifiable material along a build axis, wherein the solidifiable material solidifies at the selected distance but does not solidify between the selected distance from the exposed surface of the solidifiable material and the exposed surface of the solidifiable material.   
     
     
         42 . The method of  claim 41 , further comprising providing a linear scanning device comprising the rotating polygonal mirror and an optical system comprising at least one first mirror and second mirror between the rotating polygonal mirror and the exposed surface of the solidifiable material, the at least one first mirror and second mirror each having a rotationally symmetric curved mirror surface about their optical axis, at least one of the first and the second curved mirror surfaces having an aspheric shape, and wherein the first and the second mirror have an off-axis decentered aperture and are offset in position with respect to one another in a direction perpendicular to the scanning axis. 
     
     
         43 . The method of  claim 41 , wherein the laser has a pulse width of less than 10 −8  seconds. 
     
     
         44 . The method of  claim 41 , wherein the selectively activatable laser has a wavelength between about 700 nm and about 800 nm. 
     
     
         45 . The method of  claim 41 , wherein the selectively activatable laser is connected to an optical fiber splitter having two outputs, each output is connected to a corresponding linear scanning device, one of the linear scanning devices comprises the rotating polygonal mirror, and the other of the linear scanning devices comprises another rotating polygonal mirror, and when the laser transmits laser energy to the linear scanning devices they each deflect a beam of laser energy, and the deflected beams of laser energy intersect at the selected distance from the exposed surface of the solidifiable material.